Remove completions for (un)linkapps commands

These were deleted in cffa5a98.

bump-formula-pr: Use Parser to parse args

Support GCC 8

README: goodbye Alyssa!

And thanks for all the commits! <3

portable-ruby: increase to 2.3.1_1.

Install the latest Ruby from:
https://github.com/Homebrew/homebrew-portable-ruby/pull/55

This updates ncurses and openssl as well as more closely matching the
Apple's ruby build options.

Notably, this includes the DBM support needed for #3720.

Fix CaskAlreadyCreatedError message output

Minor edit.

components_order_cop: add post_install

formula: read runtime dependencies from more tabs.

linkage_checker: correctly handle multiple taps.

Fix upgrades of formulae with the same name in multiple taps.

As reported in:
https://github.com/Homebrew/brew/pull/3789#issuecomment-384890624

The fixes the issue mentioned in:
https://github.com/Homebrew/brew/pull/4066#issuecomment-381308153
where `brew missing` was not reading from a tab of an outdated formula.

The `installed_prefix.directory?` check is unnecessary as the following
`opt_or_installed_prefix_keg` call is already checking that when it is
necessary. In this case it's not necessary anyway as `opt_prefix` is
preferred and makes more sense on outdated formulae.

docs/Acceptable-Formulae: address feedback.

Address comments in:
https://github.com/Homebrew/brew/commit/27ec9dae5fa4c2c5b19f8bfafaefbdbb3e9a9c8c

formula_desc_cop desclength: make non-strict

Undeclared dependencies in runtime_dependencies

missing_formula: improve migration messaging.

Particularly in the cask case we can do a better job of communicating
how the new formula can be installed.

Fixes #4089.

components_redundancy_cop: make non-strict

urls_cop pypiurls: make non-strict

components_order_cop: make non-strict

Shorten some links in README.md